Marsh-marigold (Caltha palustris), also known as 'kingcups' is a medium-sized member of the buttercup family Ranunculaceae. Growing up to 80cm high, this colourful plant is found in wet meadows, marshes and wet woodlands, and grows particularly well in the shade. Its flowers are quite large - between 15-50mm in diameter, and it is one of the early flowering plants, with flowers appearing in March and lasting until June/July. In autumn, the plants die back down and overwinters with buds near the surface fo the marshy soil.

Marsh-marigold (Caltha palustris) growing along the broad at UEA.

In terms of its ecology, Marsh-marigold only grows in freshwater locations with oxygen-rich water near the surface of the soil. It is quite a good bioindicator of pollution as it avoids areas with fertiliser application and high levels of phosphate and ammonia. However, it is often associated with iron-rich seepages because iron reacts with phosphate, thus making it unavailable for plants. In the UK, Marsh-marigold is quite widespread and its population remains fairly stable, however, it is locally threatened by drainage and agricultural improvement of wet grassland habitats.

C. palustris is an extremely variable species, with many different combinations of its features having been observed. There are however, 5 main varieties that are widely recognised:

C. palustris var palustris which has yellow sepals, tricolpate pollen (pollen with 3 furrows) and is not rooting at the nodes.

C. palustris var radicans which also has yellow sepals and tricolpate pollen, but is distinguished by the plants being smaller and with fewer flowers on the stems as well as rooting at the nodes after flowering.

C. palustris var araneosa also has yellow sepals and tricolpate pollen, however the plants are larger, and have many flowers on the stem and only occurs in the fresh water tidal zones of the Netherlands.

C. palustris var alba has white sepals, usually pantoporate (with rounded opening all over the surface) pollen (although sometimes tricolpate), and is only found between 2200 and 3500m along rivulets in Afghanistan, Pakistan and the western Himalayas.

C. palustris var purpurea has magenta sepals, tricolpate pollen and is only found between 4000-5000m on alpine meadows and mossy slopes in the eastern Himalayas.

Despite some serious safety concerns, people use the flowering parts of Marsh-marigold that live above ground to try and treat a variety of ailments, including cramps, jaundice and liver problems. Some people also put Marsh-marigold directly on the skin to clean wounds and sores. However, there is no evidence that Marsh-marigold actually works to treat any of these conditions and as with all buttercups it is poisonous and can cause skin irritation, so you shouldn't try it at home!

Marsh-marigold (Caltha palustris) with a Hoverfly species assisting with pollination.

Yesterday we headed to Foxley Wood, which is about 30 minutes NW of Norwich, on an Ecology field trip. The purpose of our visit was to learn about coppicing as a management strategy, ancient woodland indicator species and to have a go at some plant identification. Unfortunately, we didn't do much of the latter due to the terrible weather.

Foxley Wood is Norfolk's largest remaining ancient woodland and over 350 flowering plants have been recorded on the site. This includes one of the UK's least known native trees: the Wild Service Tree Sorbus torminalis, which is rather inconspicuous for most of the year, until it becomes covered with white blossom in late spring and its leaves turn a coppery-red colour in autumn.

Coppicing is an ancient woodland management technique that is used extensively at Foxley Wood in order to maintain a matrix of woodland growth stages to benefit biodiversity. Coppicing involves felling the same stumps near ground level and then allowing shoots to regrow from that stump, whilst also leaving certain large trees (standards), typically mature oaks. Where coppicing occurs, the woodland is often divided into blocks and coppiced on a rotational cycle of about 15 years in order to maintain a variety of woodland ages. Historically, coppicing was used to produce numerous straight stems from each coppiced stump, which would then be used for posts, fencing and firewood.

Coppiced Hazel tree showing the numerous new stems
growing from the coppiced base.

During our wander around Foxley Wood, it was really interesting to see the different ages of coppice blocks and to be able to compare and contrast it with the ancient woodland and grazed areas. This allowed us to see first hand the effects of the different management practices and I found it particularly interesting to see the stark differences in the under storey between the coppiced areas and the ancient woodland, and also how the plant assemblages changed too.

Coppiced woodland with standards (left) compared to Ancient woodland (right)
Very different under storeys in the two areas with it being much denser in
coppiced areas and much thinner in the ancient woodland.

One of the main aims of our trip was to learn about ancient woodland indicator species (AWIs), and despite the weather, we managed to locate quite a few of the early flowering AWIs that are found at Foxley Wood. The term ancient woodland refers to land that has had continuous woodland cover since at least 1600AD, and AWIs are a group of species, typically vascular plants (but also some invertebrates and lichens), that are more common in ancient woodland than in recent sites and display a number of characteristics:

Rarely occur outside of woodland, and if they do, then they indicate a long temporal continuity of woodland cover.

Capable of growing in shade, though don't necessarily grow exclusively in shade.

Reliable indicators, in at least part of the region being surveyed.

Slow colonisers - normally have a small seed shadow, meaning that seeds don't disperse very far each year, so colonisation of new areas is slow.

There are approximately 100 plant species that are thought to be good indicators of a woodland's age, and when a woodland shows more than about 10 of these indicator species, it is likely that the wood has existed for a long time. AWIs vary between the different regions of the UK and finding one AWI species alone is not enough to determine a woodland's age, but finding combinations of AWIs suggests different things about the woodland's age.

A carpet of Honeysuckle (Lonicera periclymenum) - one of the 12 ancient
woodland indicator species that we were looking for.

While at Foxley Wood, we were on the lookout for 12 AWI plant species, and despite the dreary weather we managed to find 7 of them. One of the AWI species that we managed to find was Wood-sorrel Oxalis acetosella (also known as Common Oxalis). The Oxalis part of the binomial is due to the presence of oxalic acid within members of the genus, while acetosella is in reference to its sour taste. Wood-sorrel is a small plant that flowers between April and May. It has white flowers which droop down until the dappled sunlight reaches them, upon which the flowers tilt upwards. Each flower has 5 petals and tiny, purple veins. The leaves of Wood-sorrel are trefoil and fold down into a tent during the night, but flatten out again during the day.

Apparently, all parts of Wood-sorrel plants are edible, and the leaves (fresh or dried) are often used in alternative medicines. The leaves are said to have diuretic, antiscorbutic and refrigerant actions, and a decotion (an extract made by mashing, then boiling the plant) made from the pleasantly acidic leaves is used for high fevers, both to quench thirst and allay the fever itself. Although it may be consumed freely, excess consumption should be avoided as the oxalic salts are not suitable for all constitutions and may have unwanted effects.

Garlic Mustard Alliaria petiolata is a biennial plant in the mustard family (Brassicaceae). As it is biennial, it takes two years to complete its lifecycle. In its first year of growth, the plant grows slightly wrinkled leaves which are round in shape and smell like garlic when crushed. Flowering occurs in the second year of its lifecycle, and the plant produces white, cross-shaped flowers in a dense bunch at the top of the plant, which appear from April through to June.

At a glance, Garlic Mustard plants resemble nettles, however they can be distinguished by their smooth, hairless leaves which are somewhat heart-shaped, as well as the terminal clusters of the small, white flowers. Garlic Mustard can grow up to 1m tall and are found in a variety of habitats, including wood margins, hedgerows, roadsides and shady places. It is a native species which is found throughout the UK, being very common in England and Wales.

Garlic Mustard (Alliaria petiolata) in flower on the UEA campus - it is very
common among the nettles in the shady, wooded areas.

Garlic Mustard has a long history of use in food and medicine, being one of the oldest known spices used in cooking in Europe - archaeological evidence of its use in the Baltic dates back to 4100-3700 B.C.E. It is not really used in medicine any more, but was once used as a disinfectant or diuretic. Garlic Mustard has a variety of cooking uses, with the chopped leaves used to flavour salads and sauces, including pesto. The young leaves are preferable for this use as they provide a mild flavour of garlic and mustard; sometimes the flowers and fruits are used as well! In France, the seeds are also used, often to directly season food.

In Europe, 69 species of herbivorous insects are associated with Garlic Mustard, as well as 7 species of fungus. These include various members of weevils (especially the genus Ceutorhynchus), leaf beetles (Chrysomelids), butterflies and moths (Lepidoptera). Garlic Mustard is even a food plant for the larvae of the Garden Carpet moth.

Dendrocoelum lacteum is one of only 12 species of freshwater triclads found in Britain and Ireland.

The Tricladia are named as such due to the three main branches of the alimentary canal. Tricladia are a sub-order of the Turbellaria which sits within the phylum Platyhelminthes. Turbellaria are a globally widespread group, with new species continuing to be described. They also occur in such large numbers in some lakes that they are considered a significant components of aquatic communities.

Due to their dorso-ventral flattening, Triclads are commonly referred to as "flatworms". The adults range in size from approximately 8-15mm in length. All except one of the 12 British & Irish (B&I) species are normally found in the surface waters of lakes and streams, where they feed on a variety of prey species, including isopods (woodlice etc.), gastropods (snails and slugs) and oligochaetes (worms). Each species has its own realised niche though, which has evolved to allow coexistence. For example, D. lacteum feeds mostly on isopods, while Dugesia polychroa prefers snails and Polycelis nigra and Polycelis tenuis favour the oligochaetes.

Illustrations of 11 of the 12 species of triclad that have been found in Britain & Ireland.
Taken from "A key to the freshwater triclads of Britain & Ireland"
by T.B. Reynoldson and J.O. Young.

British freshwater triclads can be categorised into two groups: those that are found in lakes, and those that inhabit streams, however this distinction is not absolute. When they are found in lakes, triclads prefer sheltered, stony shores and are most abundant in shallow waters up to a depth of 30-35cm.

On the continent, stream-favouring species are spatially separated downstream, with Crenobia alpina (and sometimes Phagocata vitta) found near the source, with Polycelis felina occurring further downstream, followed by Dugesia gonocephala (not recorded in B&I). A similar pattern of distribution can also be seen in Britain, with P. nigra inhabiting the lower reaches of streams and rivers, however C. alpina and P. felina can cause complications as both occur along the length of short streams (although there is often spatial separation related to stream gradient).

P. nigra/tenuis (left) & D. lacteum (right)

Triclads are interesting in terms of their reproduction, because different species reproduce either sexually, asexually (by fission & regeneration) or both! Asexual reproduction is though to have evolved secondarily in the Dugesiidae and Planariidae families, to allow reproduction even when food is limiting. Another interesting thing is that pseudogamic reproduction is common among several species. This is where sperm is necessary to stimulate egg development, but no male chromosomal material is incorporated into the egg nucleus!

Of the lentic species (those living in still waters such as lakes), there are two main types of life histories: D. lacteum, Bdellocephala punctata and Planaria torva are 'annuals' that die after their spring breeding season, meanwhile P. nigra, P. tenuis, D. polychroa and D. lugubris don't die after breeding. The latter group exhibit iteroparity, breeding numerous times during their lifespan, while the former group exhibit semelparity, which is where they breed once and then die. No one really knows why these two life histories have evolved, but there are many different hypotheses, including a relation to their feeding strategies or a reduction in interspecific competition.

Dendrocoelum lacteum showing the 2 'eyes' in the top left and the internal
structures throughout. Specimen collected from the River Yare.

According to the 2009-2011 Biodiversity Audit, 5 species of triclad have been recorded on the UEA campus. One of these is Dendrocoelum lacteum, a pale and fairly large species of freshwater triclad, and one that I recently found a specimen of in a still part of the River Yare. It is a lentic species which ranges between 14-25mm in length. In the UK, it is quite common and is most frequently found in productive lakes where the calcium concentration is at least 10mg per litre. D. lacteum predominantly feeds on Asellus isopods and the triclad's distribution is closely linked with that of its prey, providing D. lacteum with a "food refuge". In order to capture intact prey, D. lacteum moves faster than the Planariid species, and has a shallow anterior pseudo-sucker. Its distribution in Britain is mostly curtailed by interspecific competition and has not yet spread into northern Scotland or the western islands.

Further reading:

"A Key to the Freshwater Triclads of Britain and Ireland with notes on their ecology" by T.B. Reynoldson and J.O. Young - https://bit.ly/2FcoUVV

Lesser Celandine (Ficaria verna) is one of the first signs of spring, with flowers appearing in late February/March. It is often present in large colonies along woodland floors, with its distinctive heart-shaped leaves forming a lush green carpet, punctuated with its bright yellow flowers. The flowers are between 2-4cm in diameter and have 3 sepals and between 7-12 petals. Lesser Celandine is plant characteristic of woodlands, and is often used as an Ancient Woodland Indicator species. However some caution must be used, as it can also be found in hedgerows, damp pastures and river/stream sides.

A atch of Lesser Celandine (Ficaria verna) growing
in the woods near the Broad on the UEA campus.

There are many different subspecies of Lesser Celandine, however Ficaria vernasensu lato is native to central Europe, north Africa and Caucasus. It is not native to North America, though it has been introduced to many parts and is now considered as an invasive species. As with Marsh-marigold, and all other species in the Ranunculaceae family, Lesser Celandine contains a compound called ranunculin, which turns into the toxin protoanemonin when the plant is wounded. Contact with damaged/crushed Ficaria leaves can cause itching, rashes or blistering and ingesting the toxin can cause nausea, vomiting, dizziness or paralysis. Due to its potential toxicity and its proliferation, Lesser Celandine has been banned or listed as a noxious weed in several US states.

It is actually possible to neutralise the toxicity of Lesser Celandine, and there are a few different methods that can be used. Simply drying out the plant is effective as the protoanemonin changes to the non-toxic anemonin, which is further broken down into non-toxic dicarboxylic acids. Cooking the plants also eliminates the toxicity, and after cooking or drying the plant can be incorporated into food or herbal medicines... Lesser Celandine has long been used by herbalists as a treatment for haemorrhoids, by applying an ointment of raw leaves as a cream to the affected area. Luckily most modern guides point out that medicines should be made from the dried herb or by heat extraction due to the toxicity of raw or untreated plant or leaf extracts.